1. Field of the Invention
The present invention relates to a position detecting apparatus for detecting the position pointed by a pointing device and, more particularly, to a position detecting apparatus which can detect, with a high degree of detecting precision, the position pointed by a pointer which is not connected to the body of the apparatus both electrically and mechanically.
2. Description of the Prior Art
A position detecting apparatus has been known in which an electric pulse current is supplied to a driving coil provided on one end of a magnetostrictive transmission medium or on the pointing end of a position pointer so as to generate a magnetostrictive vibration wave in the magnetostrictive transmission medium, and the position pointed by the pointer is detected by suitably processing the time between the moment at which the magnetostrictive vibration wave is generated and the moment at which a voltage induced by the magnetostrictive vibration wave in a detection coil is provided on the pointing end of the position pointer or on one end of the magnetostrictive transmission medium.
Also known is a position detecting apparatus in which a plurality of driving lines and detecting lines is arranged orthogonally to each other and a position is pointed by a pointer having a magnetic member such as ferrite, the driving lines are successively supplied with electric current and the detecting lines are accessed sequentially so that the position pointed by the pointer is identified by the position of the detecting line in which the highest voltage is induced.
The position detecting apparatus of the type mentioned first exhibits an appreciably high degree of detecting precision but the handling is undesirably restricted due to the presence of a cord which is essentially required for the purpose of exchange of timing signals between the pointer and the processing device. In addition, the position pointer has to be held substantially perpendicularly to and in the close proximity of the magnetostrictive transmission medium.
On the other hand, the position detecting apparatus of the second-mentioned type suffers from a problem in that the resolution of the coordinates position is determined by the pitch of the detecting lines. A higher resolution would be obtained by reducing the pitch of the detecting lines but such a reduced pitch will undesirably impair the S/N ratio of the detection signal, as well as the stability of detection performance, so that any increase in the resolution is materially impossible to obtain. In addition, it is rather difficult to detect the position right above each of the points of intersection between the driving lines and the detecting lines. Furthermore, the pointer has to be placed in the very close proximity of the lines.